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Buyers should check they are not purchasing apartments in some of the many residential blocks which Auckland Council has identified as having flammable polyethylene cores in their aluminium cladding – potentially highly combustible like London's Grenfell Tower – according to an expert.

Sean Marshall, managing director of building and construction consultants Prendos, says although New Zealand high-rise apartment blocks are much safer than Grenfell because they have fire protection measures such as sprinklers and other measures, he would be cautious when advising clients who asked about the merits of buying into one of the blocks identified by the council.

The council found 13 residential blocks in Auckland with cladding cores like Grenfell and 42 with similar panels but less combustible than Grenfell.

"I wouldn't tell them not to buy outright but I'd say 'it's in your interests to have a senior building surveyor visit the property, view the building file and write a report stating whether the building has that polyethylene core'," Marshall said.

"It's not about burning to death in a fire. It's more about the commercial risk of 'are you going to have problems on-selling a place in a block identified as having these types of panels'?", Marshall said.

At Grenfell, 71 people died after last year's fire in the 24-level block, clad in the highly flammable polyethylene-core aluminum composite panels. That sparked a New Zealand residential building cladding review, led by the Ministry of Business, Innovation and Employment and involving councils.

In Wellington, 103 building have some potentially combustible claddings as Grenfell.

Ian McCormick, the council's building consents general manager, said an extensive review had found 13 Auckland blocks had been identified with the polyethylene cores.But the council won't name those.

"We will not be providing details of the 13 buildings," a council spokesperson told the Herald.

"Last year, we conducted a comprehensive review of buildings in Auckland that potentially had elements of ACP cladding," McCormick said of aluminium composite panels.

"We have subsequently reviewed over 215 buildings. Some of these involve sites with multiple buildings which we have also individually assessed and 42 of the buildings had some degree of the less combustible ACP-FR [fire retardant] cladding panels," he said.

Most of the panels would be combustible to some extent, he said.

"Thirteen have the polyethylene core panels and a further 70 buildings have cores which have not yet been confirmed (which for the purposes of assessment we treated as ACP-PE ) or are under 25m or have a sprinkler system. In each case, as part of our review, we considered the performance of the cladding product holistically as part of the overall cladding system," McCormick said.

In many cases, ACP use was limited and associated with building features that served to reduce any potential risk, such as sprinkler systems, he said.

"In each case we have communicated this with building owners or the body corporate," McCormick said.

Some of the buildings assessed might not comply with the current building code but the council thinks a combination of fire prevention measures, fire safety systems, the extent of ACP coverage and its exposure to an ignition source do not cause immediate concerns for occupants safety, McCormick said.

Marshall said it was hard for buyers because the riskiest buildings were unnamed.

The council said the 13 did not include Orewa's Nautilus or Takapuna's Spencer On Byron because they are under repair.

"So people need to do their own due diligence," Marshall said. "People often spend more time and money having a car checked out before they buy, rather than an apartment. That's not the way it is in Europe," he said.

An expert would need to remove a panel from a building and test it, then tell a potential buyer if the block had that type of panel, he said. He knew of some Auckland high-rises which he suspected had the cores in their aluminium panel claddings but could not name any.

People often blamed councils for building issues but if they did better due diligence before buying, they could avoid many issues, Marshall said, because they would have been better informed.

The Nautilus high-rise apartment block in Orewa had an aluminium panelling which was being replaced not due to fire issues but because of weather-tightness problems, Marshall said. Prendos is involved in that work.

"We're about 40 per cent through," he said of the huge repair job on the 12-level block after a $25.07 million court payout.